1. Field of the Invention
The present invention relates to a manifold of an injection molding machine, and more particularly to a structural improvement of such a manifold in that a heating wire provided in the manifold can be easily and simply fixed on a surface of the manifold, the heating wire being used for heating a molten plastic material to prevent the molten plastic material from being solidified when the plastic material is injected from an injection cylinder into a cavity of a mold through the manifold and its injection nozzles.
2. Description of the Prior Art
In a general injection molding machine producing plastic products, a plastic raw material is introduced into and melted in an injection cylinder provided on one side of the injection molding machine, and the molten plastic material is injected into a mold. In order to smoothly and uniformly inject the molten plastic material into a cavity formed in a bottom mold, a manifold is formed in a top mold while a plurality of injection nozzles being provided at the bottom of the manifold for injecting the molten plastic material into the cavity of the bottom mold. During an injection molding process, the molten plastic material under high pressure is filled into the cavity of the mold. When the plastic material within the cavity is solidified, the top and bottom molds are separated from each other so as to remove the plastic product from the cavity.
In order to prevent the molten plastic material from being undesirably solidified in the course of its flowing from the injection cylinder into the cavity of the bottom mold, a heating wire is arranged around both the manifold and the injection nozzles. That is, the heating wire passes through a hole within the manifold to heat the manifold and so to prevent the molten plastic material from being undesirably solidified within the manifold. The heating wire is also wound around the injection nozzles to heat the nozzles. It is thus possible for the molten plastic material not to be solidified within the manifold or the injection nozzles before the molten plastic material is injected into the cavity of the bottom mold during the injection molding process.
The heating wire, however, cannot be arranged in a curved form, but is arranged in the only linear form, that is, in either a transverse or a longitudinal direction, so that there is a disadvantage in that the heating wire is incapable of delivering heat at the same thermal efficiency to plastic material injection holes arranged in the curved form. Since the heating wire cannot but be arranged in only a linear form, the whole manifold cannot be evenly heated unless a plurality of heating wire insertion holes are formed in several places of the manifold. Nevertheless, it is impossible to form the heating wire insertion holes in several places in view of the structure of the manifold, which results in using the heating wire having high thermal capacity to compensate for the inefficient function of preventing the solidification of the molten plastic material. As the result of this, there is a drawback in that the heating wire of high thermal capacity incurs a high cost.
To solve the above-mentioned problems, therefore, the present applicant has devised a prior invention, which is now allowed as Korean Patent No. 113803. In the prior invention, as shown in FIG. 1, there is formed on each of top and bottom surfaces of a manifold 1 a groove 2 into which a heating wire 3 is inserted and whose upper end is closed by a finishing material 4 made of copper having excellent thermal conductivity. Such a prior invention is being widely used because it has advantages in that the heating wire 3 can be arranged along plastic material injection holes formed within the manifold 1 to evenly transmit heat to the plastic material injection holes and thus to reliably prevent the solidification of the molten plastic material, and in that it is simpler in its installation than the forming of the heating wire insertion holes and inserting the heating wire into the holes, thereby enhancing the productivity of the manifold.
In spite of these advantages of the prior invention, however, the finishing material 4 must be so formed as to match the shape of the groove 2 and then inserted into the groove 2 by means of a pressing apparatus such as a press or a hammer, thereby complicating the manufacturing work of the manifold and raising the manufacturing cost. Also, since the finishing material 4 and the manifold 1 are different from each other in thermal characteristics such as thermal expansion and the like due to their different metal compositions, there is a problem in that the finishing material 4 is broken out of its position and thus the heating wire 3 is not fixed when the manifold 1 is used for a long time in the heated state of the heating wire 3.
Accordingly, the present invention has been made to overcome the above-mentioned problems, and it is an object of the present invention to provide a manifold of an injection molding machine, in which means for fixing a heating wire provided in the manifold of the injection molding machine is formed integrally with the manifold while being capable of easily and simply fixing the heating wire, thereby providing manufacturing convenience and economic benefit, and preventing the fixing means from failing due to the heat of the heating wire during its use.
To accomplish this object, there is provided a manifold of an injection molding machine in accordance with the present invention, the manifold comprising: a groove formed on a top surface of the manifold for inserting a heating wire thereinto while protrusions being formed on both sides of an upper end of the groove and projected from the top surface of the manifold, wherein the protrusions fix the heating wire in such a manner that the heating wire is inserted into the groove and then the protrusions are press-fitted into the inside of the groove by pressing means such as a press or a hammer.